Kim entered Japan illegally in 1958, hoping to be a student of his home country hero Rikidozan but was arrested in the following year. After being released with Rikidozan as his surety, he joined JWA and had his first match in November, 1959 under the name of Kintaro Ohki. He was one of the rookie trio along with Kanji Inoki and Shohei Baba, who joined JWA in 1960. Inoki was defeated by Ohki in his debut match.

After the death of Rikidozan in December, 1963, Kim returned to Korea and raised the popularity of the sport in his home country. Though he was brought back to JWA when Toyonobori and Inoki left the organization to start Tokyo Pro-Wrestling in 1966, Ohki was once again in the shadow of the Big 2 after Inoki returned to JWA in the following year.

He won WWA World Heavyweight Title from Mark Lewin in 1967 and became the true top star in South Korea, and prior to that, JWA was said to have "verbally promised" to Ohki to name him "Rikidozan", given that Ohki wins a world title. He never had the honor of inheriting the name, however.

He became the top star of JWA after Inoki and Baba left the group in 72 and won the prestigeous NWA International Heavyweight Title. However, JWA closed and was absorbed into All Japan Pro-Wrestling in April, 1973. Though he wrestled for All Japan for a short while, he basically became a freelancer in Japan while keeping the status as the top wrestler in South Korea. He had a famous match against Inoki in 1974 and Baba in 1975 (after Inoki had a historic famous match against Ohki, of course, Baba had to squash him in less than 7 minutes, just like he did with Billy Robinson in the following year). Ohki continued to defend the International Title in IWE and South Korea until he was "ordered by NWA" to vacate it in April, 1981 (Baba wanted the title for All Japan). While in All Japan, Ohki teamed with his student Kim Duk (Tiger Toguchi/Tiger Chung Lee) and feuded with the team of Baba & Jumbo Tsuruta over NWA International Tag Team Title.

He had not been active as a wrestler since early 1980s, and the ceremony for his retirement was held during the Weekly Puroresu magazine's all-star card at Tokyo Dome in April, 1996. Both Baba and Kim Duk were at backstage, and Lou Thesz helped Kim, who had his last public appearance in Japan on a wheelchair, to the ring for the ceremony.

While spending most of the time in the hospital, Ohki kept attending to the WWA cards promoted by Lee Wang-pyou, who is one of the top students of Ohki's. Also, Inoki recently had visited him in the hospital.

On October 26th, 2006, Kim passed away due to heart failure at a hospital in Seoul.